It is usual to print textiles with aqueous print pastes comprising pigments, dyestuffs, thickeners and other auxiliaries. The thickener or clear concentrate is used to make up a vehicle for color printing and must impart the proper flow, viscosity and rheological characteristics to the print paste. Heretofore, it has been known in the textile printing art to utilize an alkaline neutralized thickened concentrate comprising polymers or copolymers of carboxylic acids such as acrylic acid, an organic solvent, and an anionic or nonionic surfactant. Such thickened concentrates are generally utilized in the form of an aqueous paste (cut clear) which is formed by let down of the concentrate by addition to water and other auxiliaries where needed. In those cases where the concentrated thickener composition has not been preneutralized with an alkaline agent, the alkaline agent can be added to the water during let down. The alkaline agent usually used is ammonium hydroxide.
A problem encountered with such conventional thickening media is that viscosity tends to break down when electrolytes are introduced into the printing system. This problem is recognized in U.S. Pat. No. 3,940,351. Typical problem electrolytes may be sodium hydrosulfite, zinc sulfoxylate-formaldehyde, potassium citrate, caustic, salt, ammonium sulfate, sodium carbonate, sodium sulfate and others.
Previously only three methods of overcoming this difficulty existed for the printer. He could use select natural thickening agents, he could use solvent emulsions or he could "build up" his low viscosity print paste with additional synthetic thickener. But each of these methods presents additional problems.
Those natural thickening agents which are stable to electrolytes have the disadvantage of high cost and relatively long or tedious makeup. Moreover, their removal from the printed material after printing is essential if fabric with an acceptable quality is to be obtained.
The incorporation of relatively large amounts of a hydrocarbon solvent into synthetic thickener print pastes has occasionally been used to improve electrolyte stability over normal synthetic thickeners (the so-called aqueous thickeners). However, the escalating price of solvent is rapidly making this route unattractive. Moreover, air and water pollution considerations are becoming increasingly more important, not to mention health and safety hazards.
The method building up the viscosity of deteriorated print pastes with subsequent addition of thickener is an equally unattractive alternative due to the extra expense and inconvenience of making the additions.
It is an object of this invention to provide an improved synthetic thickener composition which can form thickened aqueous systems having improved viscosity stability and thickener efficiency in the presence of electrolytes. It is also an object of this invention to provide an improved thickened concentrate (clear concentrate), aqueous paste (cut clear), and textile print paste, and to provide an improved method for thickening aqueous systems.